"Things are going great," Jessa, 21, tells PEOPLE exclusively. "We are looking forward to what the future holds."

Jessa is one of 19 kids born to Jim Bob, 48 and Michelle, 47, reality stars of TLC's hit reality show 19 Kids & Counting, which gives viewers an up-front view of the family's conservative Christian lifestyle.

Both Duggar girls in relationships have chosen to wait to hold hands until they're engaged and to save their first kisses until their wedding days, something Jessa explains in the exclusive video clip below.

"What is so great is to set boundaries together at the beginning of a relationship and tell others so it sets up accountability," says mom Michelle.

Ben, who is the oldest in a family of seven from Hot Springs, Ark., says he and Jessa make up the distance by keeping in touch via Skype or FaceTime, writing letters to one another and talking on the phone.

"Jessa wrote me a letter for every single day for 20 days when we were apart," says Ben, 18. "It was so romantic."

Jessa and her sisters Jana, 24, Jill, 22, and Jinger, 20, recently published a book about relationships called Growing Up Duggar that explains in detail the girls' take on dating vs. courtship.

"It is a bittersweet time," says Michelle. "Some of the little ones don't like change but I remind them that we get to visit Josh and Anna and remind them how fun that is."

And do Jessa and Ben hope to have a large family of their own some day?

"We both want to have a big family," says Jessa. "We are talking about our goals and the future with family. We have both talked about adoption and want to adopt, too."

"Just because you are young, it doesn't mean you are not ready for life," Ben adds. "I want to encourage people to embrace adulthood. There is responsibility that comes with it and great reward. Jessa and I both have the same love for God and we really care about people. We have a lot of the same desires and goals in life."

For much more on Jill's engagement news, Jessa and Ben's courtship and photos of the couples, pick up this week's PEOPLE, on newsstands now.